Crepuscular Rays

If the air is hazy and the sun is shining in between of the clouds, you can
see impressive crepuscular rays. Bundles of light are peeking through holes in the cloud cover
and pointing radially away from the sun.
The haze, i.e. dust and water vapour in the atmosphere,
is scattering the sunlight and so makes the "path" of the sunlight visible.
The above photography was taken in the mountains of the Sierra de los Filabres in
southern Spain while frequent rain showers were falling.

See also:
M.G.J. Minnaert: "Light and Color in the Outdoors", Springer-Verlag
R. Greenler: "Rainbows, halos, and glories", Cambridge University Press